1xge

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spinqualitylabelsall models 1xge, resolution 1.90Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Dihydroorotase from Escherichia coli: Loop Movement and Cooperativity between subunits

Overview

Escherichia coli dihydroorotase has been crystallized in the presence of, the product, L-dihydroorotate (L-DHO), and the structure refined at 1.9A, resolution. The structure confirms that previously reported (PDB entry, 1J79), crystallized in the presence of the substrate, N-carbamyl-D,L-aspartate (D, L-CA-asp), which had a dimer in the, asymmetric unit, with one subunit having the substrate, L-CA-asp bound at, the active site and the other having L-DHO. Importantly, no explanation, for the unusual structure was given. Our results now show that a loop, comprised of residues 105-115 has different conformations in the two, subunits. In the case of the L-CA-asp-bound subunit, this loop reaches in, toward the active site and makes hydrogen-bonding contact with the bound, substrate molecule. For the L-DHO-bound subunit, the loop faces in the, opposite direction and forms part of the surface of the protein. Analysis, of the kinetics for conversion of L-DHO to L-CA-asp at low concentrations, of L-DHO shows positive cooperativity with a Hill coefficient, n=1.57(+/-0.13). Communication between subunits in the dimer may occur via, cooperative conformational changes of the side-chains of a tripeptide from, each subunit: Arg256-His257-Arg258, near the subunit interface.

About this Structure

1XGE is a Single protein structure of sequence from Escherichia coli with ZN, DOR and NCD as ligands. Active as Dihydroorotase, with EC number 3.5.2.3 Full crystallographic information is available from OCA.

Reference

Dihydroorotase from Escherichia coli: loop movement and cooperativity between subunits., Lee M, Chan CW, Mitchell Guss J, Christopherson RI, Maher MJ, J Mol Biol. 2005 May 6;348(3):523-33. PMID:15826651

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